Wise Water Management

The Southwest’s Counter-Attack to Climate Change

Kathryn Sorensen is a proud native of Arizona. She’s also the former head of water services for the city of Phoenix and is now research director for the Kyl Center for Water Policy at Arizona State University’s Morrison Institute.

Home facade in Phoenix, AZ

Courtesy of the City of Phoenix

She is quick to note that the cradle of civilization was in arid Mesopotamia between the Tigris and Euphrates rivers — in what is now modern Iraq — not in a northern temperate zone. “Desert cities are the oldest cities and I’m confident they will stand the test of time,” said Sorensen, who rejects the idea that people should not dwell in arid regions.

“People live where water flows and this part of Arizona has a wonderful quality of life. People will continue to move here; we just have to manage the water that we have responsibly and sustainably and build on our culture of conservation. All in all, I believe we are in good shape.”

But Sorensen isn’t naive about the threats of climate change and says she takes very seriously the need to conserve water and make changes in the built and natural environments so that her city and others in the Southwest can survive and thrive.

For good reason: The current drought in Arizona is the worst in more than 110 years of record keeping. Multiple dry winters with limited precipitation, combined with hot and dry summers, have intensified drought conditions across the state.

Aerial view of the Colorado River. Less than 50 percent of Phoenix water supplies comes from the Colorado River.

Photo courtesy of the City of Phoenix.

The Colorado River system, which provides 45 percent of the water for the Arizona Municipal Water Users Association (which includes Phoenix, Tempe, Scottsdale and other cities in the Valley of the Sun) has also experienced extensive drought conditions over the past 18 years. Due to over-allocation exacerbated by the prolonged drought, Lake Mead outside of Las Vegas has dropped to historically low reservoir levels and a water shortage has been declared for 2022, requiring use restrictions in some areas.

While she bemoans the tendency of some to pick on Arizona metropolitan areas as being unsustainable, she said she believes that cities like Phoenix and Tucson have a vibrant future. “We understand the value of water in the desert and support investment in the infrastructure that will bring certainty,” she said.

Moreover, she added, other cities elsewhere in the Southwest — now in the midst of a severe, 20-plus-year drought — can learn from what Arizona is doing. The same is true in Las Vegas, Los Angeles and San Diego, officials in those cities say. Yet there are critics, such as Jonathan Overpeck, an interdisciplinary climate scientist and the Dean of the School for Environment and Sustainability at the University of Michigan. A former Arizona resident, he warns that climate change and aridification (continued drying and heating — essentially ongoing drought) in the Southwest pose a huge threat to the region.

Sorensen acknowledges the outlook for the Colorado River — which serves the domestic, agricultural and industrial needs of 40 million people in the Southwest — is “tough.” Due to ongoing drought, its flows have dropped by more than 20 percent in recent years.

“However, it is important to put into context the fact that central Arizona is blessed with large and productive groundwater aquifers,” she said. “It has long been planned that we would protect those aquifers and only dig into and use them when we need to in times of surface water shortage.

City of Phoenix banner: In the Desert Every Drop Counts

Courtesy of the City of Phoenix

“For the most part, central Arizona has been very successful in protecting its aquifers. We have been managing and recharging them with surface water and been careful about their use so that resource will be available for future generations.”

Phoenix is located where the Salt and Verde rivers come together and was chosen long ago by native people as a place to live. “It is in an alluvial plain, where water has been deposited for eons in a productive aquifer,” she added. “So, we believe there are generations of water there, if managed carefully.”

Sorensen said water use in Phoenix has declined by 30 percent per capita in recent decades, as the city experienced rapid growth while also becoming denser.

In addition, the city recycles reclaimed water from its sewage system. While it is not yet used for drinking water, huge amounts cool the Palo Verde [nuclear power] Generating Station, which is 45 miles west of Phoenix. Treated wastewater also goes on riparian habitats, irrigates sports fields, golf courses, non-edible crops and commercial landscapes. It is also used to recharge aquifers by storing water underground. Sorenson expects the use of reclaimed water to grow in coming years.

Cynthia Campbell, the current water resources manager for Phoenix, said her city has relied on educational efforts rather than mandatory restrictions to reduce water use.

Phoenix Water Production vs. Population Growth (1990-2019)

Linear graph: Phoenix Water Production vs Population Growth (1990-2019). Phoenix water use has declined by 30 percent per capita

Graph courtesy of the City of Phoenix.

“We are proud of the fact that we have done more with education and outreach than most places have done with rebates,” she said. “We’ve grown by 400,000 people in the past 20 years, but cut our water use per person.

“That has a lot to do with new buildings using the most up-to-date fixtures, so that is very helpful. We also encourage people to think about their landscaping as well as find and fix leaks inside and outside their homes.”

The city’s water rates and zoning are geared toward encouraging xeriscaping, which uses native plants and other desert vegetation. Forty years ago, 80 percent of the homes in the city had grass lawns. Now, that figure is down to 10 percent.

Emerson School students in Phoenix, AZ planting a tree

Photo courtesy of the City of Phoenix

“Most developers are on board with xeriscaping and limiting water use,” she said. “But we still need to get some homeowners’ associations to be less restrictive about requiring grass in front yards.

“…Xeriscaping and other kinds of desert design and planting can be very beautiful. That absolutely fits into our culture of conservation. We are going to double down on our educational outreach efforts.

A house frontyard in Phoenix featuring xeriscaping, which uses native plants and desert vegetation, reduces water usage on lands

Photo courtesy of SNWA

“Besides, people here are pretty independent and don’t want to be told what they can or can’t do on their property. We try to keep it to a point where we educate and convince people that this is the right thing to do. Then we watch the results.

“We know, though, that the future will be hotter and drier so that tradeoffs will have to be made. Reducing use of water on outside landscaping is a big one, but we think people get it.”

Because temperatures of nearly 120 are no longer rare in Phoenix during the summer, the city recently created a Heat Response and Mitigation Office — the first of its kind in the nation. It is headed by David Hondula, a climate scientist formerly with Arizona State University.

According to a study commissioned by the Nature Conservancy last year, Phoenix could save lives and millions, even billions of dollars, by adapting to rising heat. The

minority communities where many households lack the means to cope with heat waves that are becoming more frequent, widespread and severe. Phoenix’s Maricopa County recorded 323 heat-related deaths in 2020.

The study also looked at the costs that can be caused by steadily rising temperatures to human health, labor productivity, electricity and roadways. Extreme heat already costs people in metro Phoenix $7.3 million every year in emergency room visits and hospitalizations due to heat-related illnesses. Maintaining roadways in the metro area costs transportation agencies over $100 million annually as streets and highways buckle, rut and crack from high temperatures.

“As Phoenix continues to urbanize and its population expands, the benefits of adapting to extreme heat may only increase, as will the consequences of inaction,” the report said. “To implement the ambitious solution scenarios and realize the associated benefits, both the public and private sector will need to play an active role.”

Planting enough trees to provide canopy for a quarter of the desert city and covering all of the area’s buildings with “cool roofs” made of materials that don’t absorb heat could help the city save billions of dollars over the next three decades, the report concluded.

Installing cool roofs on just a third of the structures in the Phoenix metro area could help save as much as $280 million annually in avoidable losses from decreased labor productivity, increased energy needs and heat-related illnesses and deaths.

The city has a two-pronged plan to deal with increased heat. They include access to cool spaces for residents now and longer-term strategies aimed at cooling the city, by tree planting, building engineered shade structures and altering the built environment in other ways to mitigate unrelenting high summer and fall temperatures.

“We need to think about policies in the zoning and building code domains, about how and where we are constructing buildings, what kinds are appropriate in which locations and the landscape requirements around them,” Hondula said.

He said the development community will play a key part in ongoing discussions to make sure the city is successful in the future. “We need to take steps today to make sure the city 20, 30 or 50 years in the future is largely going to be shaped by decisions we make over the next five to 10 years.”

Hondula is confident Phoenix can make the changes needed to deal with climate change and ensure its future economic vitality. The climate modeling studies he has seen are encouraging, if the city pulls the right levers as it continues to grow. “We can continue to urbanize, but wind up with a future that is cooler than the one we have today, even with continued global warming.”

South Nevada Water Authority Infographic: Do You Know When to Water?

Graphic courtesy of the SNWA

In Las Vegas, Doug Bennett is the Conservation Manager for the Southern Nevada Water Authority (SNWA). He said he is especially proud of the utility’s “Water Smart” program, which was launched in 2004.

“It was a voluntary program to construct dwellings that had much smaller water footprints than would be built using the code that was in place at that time,” he said.

Over time, more than 20,000 homes were built, which served as “the trailblazer for the U.S. Environmental Protection ‘WaterSense’ home program.

“We did it with the help of the homebuilders. One of the lead builders on that was KB Homes, which has a strong sustainability bent. They aren’t afraid of trying some things that are outside the norm of the industry and building projects that have innovative ideas embedded in them. KB was one of our critical partners, but we had others like Pulte.”

The program was so successful that it was used as a model for area building codes. “Now all homes in Nevada have to be built with WaterSense-labeled plumbing fixtures and Energy Star appliances are pretty much the norm,” he added.

Moreover, landscape design restrictions, many of which date to 2003, take care of much of the outdoor water use component. “Back then, we implemented new codes that said you couldn’t plant grass in the front yard of a new home and you couldn’t plant more than 50 percent of the area in the backyard as lawn grass,” he said. That effort has resulted in the removal of an impressive 200 million square feet of turf grass and saved 163 billion gallons of water. Summer water restriction rules include Sunday bans and no watering from 11 a.m. to 7 p.m., the hottest period of the day and when irrigating is least effective. In 2021, more than 1,900 water waste fines were issued by agencies for non-compliance, which brought in $560,000.

Southern Nevada crew removing grass

Photo courtesy of the SNWA

“To be frank, most of the residential water use at a residential home in that era was on lawns,” he said. “People were using more water on turf than for anything else in the household. It dwarfed indoor use like showers or washing machines. Research showed lawns required about 10 feet of water each year, and we live in a region where four inches of annual rainfall is typical.”

Cutting lawn sizes, plus a move in the housing industry to greater densities and building to the “WaterSmart” program made post-2004 houses 50 per cent more efficient.

Current rules include prohibition of all grass in front and backyards of new residential homes and commercial developments, a ban on high-water use, evaporative cooling in new commercial development and prohibition of new golf courses in the Las Vegas Valley Water District Service Area.

Las Vegas works with cities around the globe on ways to cut water use. That includes Singapore, which is the only city that currently recycles more water than Las Vegas, Bennett noted.

“We are always interested to hear what is going on in other water-stressed regions,” he said. “One of the exciting things about the public water industry is that everyone is eager to share their ideas. There is no competitive advantage to keeping secrets about things that work well.”

Water use in the SNWA is now 110 gallons per person per day and the goal is to trim that to 86 gallons per person per day by 2035. “By making additional changes, we hope to wind up with a water footprint that we think will keep us sustainable,” he said. “We will continue to be very aggressive in our water conservation measures with the expectation that the shrinking Colorado River is not going to provide more water in the future.”

Steffen Lehmann is a professor of Architecture & Urbanism at the University of Nevada Las Vegas and founding director of the university’s Urban Futures Lab. He is less optimistic about the region’s future and notes that Las Vegas is the fastest-warming city in the United states.

Lehmann’s lab is researching nature-based solutions that can be up-scaled and transferred to other cities. “There are many exciting new concepts and solutions emerging, from “cool materials” that keep buildings cooler, to new ways to activate natural cross-ventilation (reducing the need for air-conditioning), to behavior change that increases waste avoidance, to new planning concepts that integrate the intersection domains of food-water-energy,” he said. “Some of the new solutions are actually ‘old’ solutions that used to be common sense a long time ago and some deliver a payback of the investment in less than five years.”

He proposes “regreening” the city, making it an urban forest with native plants and trees to deal with the threat of urban heat islands, such as Las Vegas’ famed Strip.

“The way we build, with concrete roofs and black tiles, is the worst as it absorbs solar radiation and traps the heat, making the city a baking oven during heat waves,” he said.

He stresses that the region needs to reduce its dependency on driving because 35 percent of heat-trapping greenhouse gas emissions in Southern Nevada come from transportation. Building in a more mixed-use and higher-density manner would help reduce energy use and make neighborhoods more walkable and compact, following what he calls a polycentric urban structure model.

He would also limit metro Las Vegas’ urban growth boundary and seek ways to reduce the high use of air-conditioning. “Let us be honest, for half the year we could get away without air-conditioning,” he said, noting that Las Vegas has more solar radiation potential than any other city in the country. “As long as all energy generated is not coming from renewable clean sources like solar, we need to reduce our use of air-conditioning.”

Brad Coffey is the Water Resources Manager for Southern California’s Metropolitan Water District (MWD), a regional wholesaler and the largest supplier of treated water in the country. A cooperative made up of 14 cities, 11 municipal water districts and one county water authority, it provides water to 19 million people in a 5,200-square-mile service area.

About 25 percent of the water used in Southern California typically comes from the Colorado River. Another 30 percent originates in the Northern Sierra. The remaining 45 percent comes from a mix of what are considered local supplies, which includes the city of Los Angeles’ eastern Sierra water deliveries as well as recycling, desalination and groundwater supplies.

Coffey said a drought in the 1980s “changed the calculus of what we do to recognize that the next person who lives in Southern California and the next dollar of economic activity can’t come from more and more imported supplies.

“We developed an integrated resources plan that aimed to transform the region from being about 60 percent dependent on imported supply to about 40 percent dependent on imported water supply and 60 percent local supply and conservation, recycled water and the like.”

The Orange County Water District Groundwater Replenishment System is the world’s largest effort for potable water reuse.

Photo courtesy of Orange County Water District

Fast forward 30 years and he said the MWD is now working on a regional recycled water program that would transform the largest discharge of treated waste water in southern California into an engine for groundwater replenishment. It would have a cycle of water that becomes far less dependent on a snowpack-dependent source.

He praised the Orange County Water District (OCWD) for spearheading consumer acceptance of recycled water with its “Water Factory 21” project, which took treated wastewater from the Orange County Sanitation District, recycled it, blended it with imported water and injected it into 23 wells to combat seawater intrusion. It has since evolved into the district’s Groundwater Replenishment System, the world’s largest effort for indirect potable (drinkable) reuse.

Orange County Water District technician working at a water pump station

Photo courtesy of the Orange County Water District

Thanks to scientifically proven advances in water technology, the system takes highly treated wastewater that would

have previously been discharged into the Pacific Ocean and purifies it using a three-step advanced treatment process.

In addition, the OCWD’s Green Acres Project (GAP) is a water reuse effort that provides recycled water for landscape irrigation at parks, schools, golf courses and industrial uses, such as carpet dying; toilet flushing; and power generation cooling.

Coffey said the amount of recycled water in the MWD in recent years has ranged from 10 to 12 percent, more than a 10-fold increase from the 1980s, when the average use of potable water per person in Southern California was about 200 gallons per day. That figure has dropped to around 120 gallons per person per day, a decline of 40 percent. But he said a 20 percent recycled figure is within striking distance.

Currently, the district’s Advanced Purification Center is a 0.5 million gallon per day demonstration facility that will generate information needed for the potential future construction of a full-scale recycled water plant. It uses a unique application of membrane bioreactors designed to significantly increase efficiency in water recycling.

Scientists and engineers are testing the process, utilizing full-scale treatment modules, to ensure the resulting purified water meets the highest water quality standards. Once approved by regulators, this innovative process could be used throughout California and even applied around the globe.

Fully constructed, it would provide about 150 million gallons of water a day, enough for about 500,000 homes. Purified water from the advanced treatment facility would be delivered through up to 60 miles of new pipelines to the region’s groundwater basins, industrial facilities and two of MWD’s treatment plants.

While water conservation and treatments continue to advance — the elephant in the room remains climate change.

“The Southwest may well have a grim, dry and hotter future in front of it,” said the University of Michigan’s Overpeck. “And no one really knows how big those all-important aquifers, such as the Colorado River Basin, are.

“Last year, the all-time temperature record was broken when 130 degrees was reached in the Mojave Desert’s Death Valley and I’m worried we will have long periods of temperatures in the 120 range in coming years,” he said. In addition, power shortages triggered by extreme heat would be problematic, to say nothing of dust storms, more wildfires and more smoke and other pollution, all of which will hit poor communities hardest.”

“Fortunately, there are a lot of smart people working on these problems,” he concluded. “The question is do politicians there have the political will to tackle them. Regardless, there is a lot to be concerned about.”

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